Capacitive micromachined acoustic transducer

Abstract

A micromachined capacitive acoustic transducer including an electrode formed by a perforated plate and another electrode formed by a shallowly corrugated membrane anchored at one or more positions on the substrate which also supports the said perforated plate is described. Also disclosed includes: a fixed perforated plate; a movable shallowly corrugated membrane having holes to form acoustic filter to a certain frequency or a range of frequencies spaced from the perforated plate that is anchored in one or more location but loose at other locations; a support structure in the perforated plate maintaining the minimum separation between the membrane and the perforated plate near the perimeter.

1. A micromachined miniature acoustic transducer including
 a capacitor formed by a perforated plate and a membrane; 
 the perforated plate having well defined perforation holes that serves as one electrode of the capacitor; 
 a shallowly corrugated membrane that is anchored at one or more locations to form another electrode of the said capacitor; the length of corrugation for the said membrane is predetermined based on the desired sensitivity requirement; 
 a substrate on which the said membrane and the said perforated plate are anchored; and 
 the said membrane having an anchoring structure that forms a tuning fork with the said perforated plate. 
 
   
   
     2. A micromachined miniature acoustic transducer as in  claim 1  in which the said perforated plate has a plurality of spacers that define the minimum separation of the said membrane from the said perorated plate. 
   
   
     3. A micromachined miniature acoustic transducer as in  claim 1  in which the said membrane is shallowly corrugated; the said membrane is further anchored onto the said substrate at one or more locations. 
   
   
     4. A micromachined miniature acoustic transducer as in  claim 1  in which the said membrane is loosely supported on the said substrate at positions where the said membrane is not anchored onto the said substrate. 
   
   
     5. A micromachined miniature acoustic transducer as in  claim 1  in which the said membrane and the said perforated plate having pre-defined through holes that are arranged in combination to form a low-pass filter for passage of slow varying ambient pressure. 
   
   
     6. A micromachined miniature acoustic transducer including
 a capacitor formed by a perforated plate and a membrane; 
 the perforated plate having well defined perforation holes that serves as one electrode of the said capacitor; 
 a shallowly corrugated membrane that is anchored at one or more locations to form another electrode of the said capacitor; the length of corrugation for the said membrane is predetermined based on the desired sensitivity requirement; 
 a substrate on which the said membrane and the said perforated plate are anchored; and 
 the said membrane is anchored onto the said substrate in such a way that the bending stress increases with the bias voltage, thereby maintaining the relative stable sensitivity. 
 
   
   
     7. A micromachined miniature acoustic transducer as in  claim 6  in which the said perforated plate has a plurality of spacers that define the minimum separation of the said membrane from the said perorated plate. 
   
   
     8. A micromachined miniature acoustic transducer as in  claim 6  in which the said membrane is shallowly corrugated; the said membrane is further anchored onto the said substrate at one or more locations. 
   
   
     9. A micromachined miniature acoustic transducer as in  claim 6  in which the said membrane is loosely supported on the said substrate at positions where the said membrane is not anchored onto the said substrate. 
   
   
     10. A micromachined miniature acoustic transducer as in  claim 6  in which the said membrane and the said perforated plate having pre-defined through holes that are arranged in combination to form a low-pass filter for passage of slow varying ambient pressure. 
   
   
     11. A micromachined miniature acoustic transducer including
 a capacitor formed by a perforated plate and a membrane; 
 the perforated plate having well defined perforation holes that serves as one electrode of the capacitor; 
 a shallowly corrugated membrane that is anchored at one or more locations to form another electrode of the said capacitor; the length of corrugation for the said membrane is predetermined based on the desired sensitivity requirement; 
 a substrate on which the said membrane and the said perforated plate are anchored; and 
 the said membrane has holes that are defined to form acoustic filter to a certain frequency or a range of frequencies; the size of holes is uniform, non-uniform, or a spread according to the filtering needs. 
 
   
   
     12. A micromachined miniature acoustic transducer as in  claim 11  in which the said perforated plate has a plurality of spacers that define the minimum separation of the said membrane from the said perorated plate. 
   
   
     13. A micromachined miniature acoustic transducer as in  claim 11  in which the said membrane is shallowly corrugated; the said membrane is further anchored onto the said substrate at one or more locations. 
   
   
     14. A micromachined miniature acoustic transducer as in  claim 11  in which the said membrane is loosely supported on the said substrate at positions where the said membrane is not anchored onto the said substrate. 
   
   
     15. A micromachined miniature acoustic transducer as in  claim 11  in which the said membrane and the said perforated plate having pre-defined through holes that are arranged in combination to form a low-pass filter for passage of slow varying ambient pressure.